Purple nutsedge management with allelopathic sorghum

Purple nutsedge (Cyperus rotundus L) is most troublesome and noxious weed. Sorghum allelopathy has the potential to suppress many weeds; hence, this study was done to explore the potential of sorghum allelopathy in purple nutsedge management in pot culture and field studies. In laboratory bioassay, Sorgaab (sorghum water extract) 0, 5, 50 and 100% was compared to acetachlor (Dechlor 50-EC) and weedy check. In field trial, irrigated and rainfed sorghum cv. JS-263 was harvested at maturity and incorporated into the soil as under (i) Control (without sorghum), (ii) Pre-flowering stage, (iii) Uprooted at maturity,(iv) Roots at maturity, (v) Roots+stem at maturity, (vi) Roots+leaves at maturity and (vii) Whole plants at maturity. Sorghum treated plots were sown with wheat or kept fallow in the following summer season. Laboratory study showed that Sorgaab (100%) was the best treatment in suppressing the shoot length and dry weight of purple nutsedge. Field study showed ∼100% reduction in purple nutsedge population. Three allelochemicals viz., m-coumaric acid, caffeic acid and chlorogenic acid were identified in sorghum by gas chromatography.